Chemistry 11
Ch 5.1-5.2 notes
Name: __________________
Blk: ______ Date: ________
Ch 5.3a Mole: Mass Relations
Objective: To determine the number of moles and mass of a substance using molar mass.
 Since 1 mol of X has a mass of (molar mass of X) g , we can obtain the following conversion
factors.
 Note: The correct unit for molar mass is gram, but Ms. Chan wants you to write g/mole for the
purpose of unit cancellations.
Mole: Mass Relations:
1 mol
(Molar mass of X) g
or
(molar mass of X) g
1 mol
Steps:
1. Find the molar mass of the sustance.
2. Start with the given amount.
3. Use the correct conversion factor.
Recap: Unknown = Given x Conversion Factor
Examples:
1) What is the mass of 5.21 mol NH3?
Step 1: Molar mass of NH3 = _____________________
Step 2: Given x conversion factor:
2) Determine the number of moles of H2O in 1000. g of H2O.
Step 1: Molar mass of H2O =_________________
Step 2: Given x conversion factor:
3) If 0.140 mol of acetylene gas (C2H2) has a mass of 3.64 g, what is the molar mass of
acetylene?
NOTE: Molar mass can be calculated by dividing the mass of the substance by the number of
moles contained in the substance, i.e. MOLAR MASS is a DERIVED QUANTITY, and g/mole is a
DERIVED UNIT.
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Classwork:
1) What is the mass of 1.46 x 102 mole of NaBr?
2) Determine the number of moles of C2H5OH in a 355g sample of C2H5OH.
3) What is the mass of 8.80 mole of bromine gas?
4) How many moles of helium gas are present in a balloon containing 75.0g of helium gas?
5) During recrystallization, 15.5g of copper (II) sulphate pentahydrate is obtained. How many
moles of copper (II) sulphate pentahydrate crystals are separated from impurities?
6) In the reaction of iron and oxygen, 0.350 moles of 55.8g of product were produced. Determine
whether FeO or Fe2O3 is the product in the reaction by comparing their molar masses with that
of the product.
Assignment: Hebden: p.82 #8a-g, #9a-i,# 10
HOLY MOLLY JOKES 
Q: What’d Avogardo say to Shakespeare?
A: “To MOLE or not to MOLE, this is the question.”
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